Stress-corrosion resistant proppant for oil and gas wells

Abstract

Aluminous proppant media in the form of sintered bauxite spheres containing silica are improved in resistance to stress corrosion by inclusion of zirconia in the mix prior to firing in the amount of a silica to zirconia ratio of from 6/1 to 20/1.

What is claimed is: 
     
       1. In a proppant medium composed of spherical particles of a sintered composition of alumina, silica, and the impurities associated with bauxite, such impurities selected from the group consisting of alkali and alkaline earth, oxides, iron oxide, and titanium oxide, the improvement wherein there is at least 15% silica in the composition and zirconium oxide is present in the ratio of between one part of zirconia per twenty parts of silica to one part of zirconia per six parts of silica by weight, the proppant spheres as fired, consisting essentially of mullite, alumina, and glass, the silica content in the weight ratio being calculated as SiO 2  combined in the mullite phase and SiO 2  in the glass phase, and zironia content calculated as ZrO 2  and present in the glass phase. 
     
     
       2. A proppant as in claim 1 with up to 19% silica and from 1 to 2% zirconia, made by the pelletization and sintering of bauxite to which a source of zirconia has been added. 
     
     
       3. A proppant as in claim 1 made from bauxite and a source of zirconia selected from the group consisting of zirconia, zirconium silicate, and zirconium salts.